Melanoma is the most serious of the common skin cancers. New Zealand has one of the highest rates in the world. Most melanomas are found early and are cured by surgery. This guide explains what happens after a melanoma has been found. It covers the second operation that removes a safety margin of skin, the sentinel node biopsy that checks the nearest lymph gland, recovery, the risks, and how you are followed up.

What is melanoma?

is a cancer of the pigment cells of the skin. Most start as a new spot, or in a mole that changes. The more common skin cancers tend to stay where they start. Melanoma can spread to the lymph glands and to other organs if it is not removed early. New Zealand and Australia have the highest rates of melanoma in the world1. Skin cancer is the most common cancer in Aotearoa New Zealand. About 2,800 invasive melanomas are found in a typical year. In 2022 there were 3,095 invasive melanomas and 317 deaths from melanoma2. Most melanomas in New Zealand are first noticed by the person themselves3.

How is melanoma diagnosed?

A suspicious spot is removed whole, with a narrow rim of normal skin of about 2 mm. It is sent to the laboratory45. This is called an excision biopsy. Taking only a piece of the spot, with a punch or a shave, can miss the diagnosis or misjudge its depth. So it is avoided when melanoma is suspected6. If the report confirms melanoma, you will be offered a second operation.

What the pathology report means

The most important measure is the . It is how deep the melanoma reaches, in millimetres. Alexander Breslow introduced it in 1970, and it is still the strongest single guide to the outlook789. Melanomas are grouped as thin (1 mm or less), medium (over 1 mm to 4 mm) and thick (over 4 mm). The report also says whether the surface is ulcerated, or broken, and how many cells are dividing. Both matter for the outlook98.
Some melanomas are found while still confined to the top layer of the skin. This is . It has not spread, and complete removal with a small margin cures it5.

Why a second operation?

The second operation is a . The surgeon removes a measured of normal-looking skin and fat around the biopsy scar. The cut goes down to the layer over the muscle. This clears any cancer cells left behind5. The width of the margin depends on the Breslow thickness. The Australian and New Zealand melanoma guideline, revised in 2018 by Cancer Council Australia, advises5:
  • melanoma in situ: 5 to 10 mm;
  • up to 1 mm thick: 1 cm;
  • over 1 mm to 2 mm: 1 to 2 cm;
  • over 2 mm to 4 mm: 1 to 2 cm;
  • over 4 mm: 2 cm.
These margins come from large trials. For thick melanomas, removing 4 cm instead of 2 cm did not improve survival, even after nearly 20 years1011. For melanomas over 2 mm, removing only 1 cm instead of 3 cm led to more melanoma coming back nearby. In the long run it also led to more deaths from melanoma1213. Wider margins also mean bigger wounds. In one trial, wound problems rose from 8 to 15 in 100 with the wider margin13. In another, 2 cm margins needed a flap or graft more than twice as often as 1 cm margins14. Whether 1 cm is enough for thicker melanomas is being tested in the MelMarT-II trial. Its results are awaited15.
Most wounds are closed directly. Where the skin is tight, such as the lower leg, scalp or face, a or a may be needed.

What is a sentinel node biopsy?

Fluid from the skin drains through lymph channels to the lymph glands, or nodes. The first node that a melanoma drains to is called the sentinel node16. A finds that node and removes it. It is then checked under the microscope for cancer cells.
It is offered when the melanoma is 1 mm thick or more. It is also offered from 0.8 mm if there are other high-risk features, such as ulceration517. Thinner melanomas very rarely spread to the nodes, so the test is not needed. For melanomas under 0.8 mm, the chance of cancer in the node is low; between 0.8 and 1 mm it is a little higher, which is why the test is considered from that thickness17. Across the melanomas for which the test is usually done, it is about 1 in 518.
The biopsy is a staging test. Whether the node is clear is a strong guide to the outlook. It also decides whether you are offered further treatment1817. In the largest trial it did not change survival for the group as a whole. It did find the people who needed further treatment earlier18.

What happens on the day

The two operations are usually done together, under a general anaesthetic. Most people go home the same day or the next morning. On the morning of surgery, or the afternoon before, a tiny dose of a radioactive tracer is injected into the skin around the biopsy scar. A scan then shows which node, or nodes, take up the tracer. The skin can drain to nodes that cannot be predicted from the site of the melanoma, sometimes to unexpected places. So the scan is advised for everyone having the biopsy19. A three-dimensional scan finds more nodes and makes the biopsy possible more often in the head and neck20.
In theatre you are given a dose of antibiotic at the start. A blue dye is injected around the scar as well. The surgeon uses a hand-held probe that detects the tracer. The node is found through a small cut and removed2122. With the tracer, with or without the dye, the node is found in about 98 to 99 in 100 people23. The wide excision is then done. Sometimes a small drain is left in the node wound for a few days.

Recovery

The wounds are covered with dressings. Keep them dry for the first two days. The node wound is usually closed with dissolving stitches under the skin. The stitches in the wide excision wound are removed at one to two weeks, unless dissolving ones were used there too. The blue dye turns the urine blue or green for a day or two. It can also leave a faint blue mark in the skin for some months. You are seen in clinic at about two weeks. The wounds are checked and the result of the node biopsy is discussed. Most people are back at light work within a week or two. You can drive when you can brake and turn comfortably, usually after one to two weeks. Sport and heavy lifting wait until the wounds have healed. For wounds in the groin or armpit that is usually four to six weeks.

Risks

Any operation can be followed by bleeding, infection, slow healing or a thick scar. The risks of the node biopsy depend on the site. In a large trial, about 1 person in 10 had a problem after the biopsy alone24. A recent series found problems in about 17 in 100 within three months. The most common were a fluid collection under the wound (9 in 100), infection (5 in 100) and swelling of the limb (4 in 100, counted over the first year)25. Wound infection is more common in the groin than in the armpit or neck26. Lasting is swelling of the arm or leg because lymph fluid cannot drain. It affects about 6 in 100 people after a node biopsy alone. After removal of all the nodes it affects about 1 in 427. A serious allergic reaction to the blue dye is very rare. It happens in about 1 in 1,600 procedures overall, and far less often in melanoma surgery, where a small dose is placed in the skin28.
The test can also miss disease. In pooled studies about 1 node biopsy in 8 was falsely negative. Even so, fewer than 5 in 100 people with a clear node later develop cancer in that node area29.

If the node contains melanoma

This is stage III melanoma. Removing all the other nodes in the area used to be routine. Two large trials have shown that this does not improve survival, and it causes more lymphoedema. So most people are now followed with regular ultrasound scans of the node area instead273031. Ultrasound finds a growing node more reliably than examination by hand32. You will be referred to a medical oncologist. Your case is discussed at a team meeting to consider drug treatment that lowers the chance of the melanoma returning33.

Follow-up and looking after your skin

After a melanoma you are checked regularly, for two reasons. The melanoma can come back, most often near the scar or in the nodes. You are also at higher risk of a second melanoma. In one large series, for every 1,000 people treated for early melanoma, 229 had the melanoma come back within ten years, and 61 developed a new one34. About 3 in 4 recurrences are found by the person or their partner, not by the doctor35. The risk of another melanoma is about nine times that of the general population. It is highest in the first year and stays raised for more than 20 years3637. Visits are closer together in the first few years and then spaced out. Check your own skin and the node areas every month. Protect your skin from the sun: slip, slop, slap and wrap whenever the UV index is 3 or above38.

What is the outlook?

Most people treated for melanoma are cured. Five years after diagnosis, most people with stage I or stage II melanoma are alive and have not died from it; for stage III the outlook varies widely between its substages, from very good to poor9.
The outlook for melanoma that has reached the lymph nodes is changing quickly. Immunotherapy drugs, given before or after surgery, have improved the results in recent trials. In one trial for melanoma that had formed a lump in the nodes, two immunotherapy drugs were given before surgery. At one year, more of those people had no return or growth of the melanoma than people who had surgery first and one drug afterwards39. In another study, most people whose nodes responded well to the drugs did not need the larger node operation at all4041. These treatments are new, so the survival figures for stage III are still changing. Your treating team can tell you what applies to you.

When to seek help

Contact your GP or the clinic if:
  • a wound becomes red, hot, swollen or leaks, or you develop a fever;
  • you notice a new lump near the scar or in the armpit, groin or neck;
  • an arm or leg starts to swell;
  • you find a new or changing dark spot anywhere on your skin;
  • on the day of surgery, you develop a rash, wheeze or feel faint after the blue dye.
Your GP can refer you to a plastic surgeon. Melanoma care in New Zealand is planned by a team of doctors, and your follow-up plan is set by your treating team.